There won't be any harm in burning peat, but, unless you have air from below the fire and the fuel on a grate, you won't have much success burning peat well. In an open fireplace you simply use an elevated grate to get a decent burn; in an insert to get a good burn you would have to have one designed for peat or coal. Having said all this, give it a try, it may work out ok for you. No, there are no significant differences as far as soot goes, usually just more powdery soot from peat vs. tarry creosote from wood. The main difference is the smell, you'll either love it or hate it.

Thanks. Hadn't thought about a different grate.

Does peat smell like coal.